Pneumatic piston actuator



HAROLD E. WA RsTL ER ATTORNEY Oct. 27, 1964 H. E. wARsTLER PNEUMATICPIsToN AcTUAToR Filed Oct. 22,

United States Patent Oiiice 3,153,988 Patented Get. 27, 1964 3,153,988PNEUMA'HC PISTON ACTUATR Harold E. Warstler, Bloomington, Ind., assignorto Robertshaw Controls Company, a corporation of Delaware Filed Oct. 22,1962, Ser. No. 232,125 4 Claims. (Cl. 92-119) This invention relates tomeans for converting a pneumatic signal to linear motion comprising apiston actuator having a novel pressure porting and swivel structure.

It is an object of this invention to provide a piston actuator having anovel swivel mounting.

Another object of this invention is to provide a piston actuator havinga novel swivel mounting, wherein said mounting includes integralpressure connections.

These and other objects of this invention will become more fullyapparent with reference to the following specication and drawings whichrelate to a preferred embodiment of the present invention.

In the drawings:

FIGURE l is a top plan view of the invention in partial cross-section;

FIGURE 2 is a side elevation of the invention; and

FIGURE 3 is a cross-section taken along line 3 3 of FIGURE 2.

Referring in detail to the drawings, the piston actuator of the presentinvention is shown as comprising opposed upper and lower bell housings12 and 14, respectively, having opposed juxtaposed flanges 16 and 18secured together by a plurality of peripherally spaced bolts 20.

In the absence of a specific pilot controller (not shown) forcontrolling the actuation of the piston actuator, the top of the upperbell housing 12 is closed olf by a cover plate 22 secured to the upperhousing 12 by a plurality of hold-down screws 24.

The upper housing 12 and the cover plate 22 are peripherally recessed atdiametrically opposed locations 26 whereby the lower tips 28 of a pairof dependent trunnion arms 30 is located one in each of the saidrecesses 26 immediately adjacent the upper bell housing 12. The trunnionarms 30 are integral with a cantilever type mounting bracket 32including a mounting plate 34 which is adapted to be bolted to anysuitable support (not shown) via a plurality of bolt-holes 36.

As shown in FIGURES l and 3, the upper end of the upper housing 12contains integral ow ports 38, 40 and 42 comprising left and rightexternal and central or internal ports, respectively. The left and righthand external pressure ports 38 and 40 are adapted to be connected tosuitable sources of signal pressure including a variable input pressureand a main or supply pressure for operation of any suitable pilotpositioner or the like which may be placed thereon in the position ofthe cover plate 22. For this purpose, each of the external pressureports 38 and 40 are connected via transfer ports 44 and 46,respectively, to recessed internal coupling sockets 48 and S0 in thesaid upper housing 12 beneath the cover plate 22.

The tips 28 of the trunnion arms 30 include coaxially disposed tappedbores 52 and 54 which are adapted to receive tirst and second trunnions56 and 58, respectively, on which are provided externally threadedportions 60 and 62. The trunnions 56 and 58 are indexed with respect tothe said bores 52 and 54 by means of integral hex-heads 64 and 66,respectively, which are adapted to be turned up, via the threadedportions 60 and 62, respectively, into juxtaposition with therespectively associated tips 28 of the trunnion arms 30.

The first and second trunnions 56 and 58 include smooth cylindricalportions 68 and '70, respectively, which are adapted to fit directlyinto the left and right hand external pressure ports 38 and 40,respectively. A rst and second pair of O-ring seals 72 and '74,respectively, are provided on the cylindrical portions 68 and 70 of thesaid trunnions, whereby the said upper housing 12 is rotatablyjournalled on the trunnions 56 and 58 by its external pressure ports 38and 40, respectively.

The first and second trunnions S6 and 58, respectively, are providedwith axial bores 76 and 78 which extend completely therethrough tocommunicate directly with the said external pressure ports 38 and 40 andprovide means whereby external pressure connections may be made with thesaid external pressure ports 38 and 40. Filter screens 80 and 82 may beplaced in counterbored coupling recesses 84 and 86, respectively, in thefirst and second trunnions 56 and 58, respectively, whereby impuritiesare prevented from entering the said pressure ports 38 and 40. Plasticclosure caps 88 and 90 may be inserted in the coupling bores 84 and 86,respectively, when external connections have not yet been made, tofurther prevent impurities from entering any portion of the pressurecouplings of the piston actuator 10.

The inner wall 92 of the upper bell housing 12 defines a cylinder whichhouses a hollow conformally shaped piston 94 over which is draped amotor diaphragm 96.

The motor diaphragm 96 has its outer periphery 98 clamped between theflanges 16 and 18 of the upper and lower bell housings 12 and 14,respectively, and is held against the top of the piston 94 by means of abutler plate 100 which is coextensive with the top of the said piston.

The piston 94 is mounted on a piston rod or actuator output shaft 102 bymeans of an integral, inwardly extending, internally threaded collar 104which interacts with an externally threaded bushing 106 fixed on theupper end of the shaft 102, an integral shoulder 108 on the upper endofthe bushing 106 is brought into juxtaposition with the butler plate100, when the piston 94 is turned-up on the said bushing 106 via thecollar 104, to thereby force the bufer plate hard against the motordiaphragm 96 and the top of the piston 104 and positively retain themotor diaphragm in place.

In addition, the butler plate 100 also serves to prevent the motordiaphragm 96 from engaging the upper limits of the cylinder at theinternal shoulder 110 thereof and thereby prevents undue wear on thesaid diaphragm.

The piston rod or actuator output shaft 102 is slidably bushed in ametal sleeve 112 integral with the lower end of the lower bell-housing14. A pair of nylon bearings 114 and 116 are inserted in the bore 118 ofthe sleeve 112 to effect a low friction mounting for the said shaft 102.A suitable output coupling means is provided on the lower tip of theoutput shaft 102, externally ot the lower bell-housing 14.

The piston 94 is biased inwardly to its uppermost position in the upperbell-housing 12 by means of a range spring 122, in the form of a helicalcompression spring, having one end juxtaposed with the lower inner endwall 124 of the lower bell-housing 14 and the other end juxtaposed withthe inner top end wall 126 of the piston 94.

The lower limit of piston travel is determined by means of a pair ofstops 128 and 130 slidably mounted, respectively, in a pair ofvertically and diametrically disposed slots 132 and 134 in the wall ofthe lower bell-housing 14, the said stops extending internally of thesaid lower bell-housing. The stops 128 and 130 are adjustably securedalong the slots 132 and 134 by means of set screws 146 and 138,respectively, which cause washers 140 and 142, respectively, tocooperate with the respective stop members 128 and 130 to clamp againstthe walls of the lower bell-housing 14 adjacent the said slots.

Once the stops 128 and 130 have been positioned in the slots 132 and134, respectively, the lower limit of travel of the piston 94 is setsince the lower rim 144 of the said piston Will engage the said stops atthe said lower limit.

Since the present invention primarily resides in the swivelling andpressure porting arrangements of the piston actuator 10, it will suce tosay that, in operation, the position of the pis-tn 94 in the upperbell-housing 12 is determined by the magnitude of the pressure admittedvia the central pressure port 42 which generates a force on the piston94 acting against the force of the range yspring 122 to establish anequilibrium position. Thus, by varying the pressure admitted above thepiston 94 by the central pressure port 42, the position of the piston 94and hence, of the output coupling 121i, on the output shaft 102, isselectively controllable.

As can be seen from the foregoing speciiication and drawings, thisinvention provides a new and novel cornbined pressure porting and swivelstructure for pneumatic piston actuators.

It is t0 be understood that the embodiment shown and described herein isfor the purpose of example only and is not intended to limit the scopeof the appended claims.

What is claimed is:

1. In a pneumatic piston actuator including a cylinder, a piston in saidcylinder and an output shaft connected with said piston; means forpivotally mounting said cylinder and connecting said piston actuatorwith sources of control pressure comprising a bracket, a pair ofdependent trunnion arms on said bracket each having a tapped bore in thefree end thereof, said bores being coaxially disposed, a pair ofdiametrically opposed fiow ports in said cylinder adapted to be placedin registry with said tapped bores, and a pair of trunnions threadablysecured in said bores and rotatably received in said ilow ports, each 0fsaid trunnions including pressure coupling means and pressure portsextending therethrough from said coupling means, whereby said cylinderis pivotally mounted on said trunnions and said How ports are connectedwith said pressure coupling means via said pressure ports in saidtrunnions.

2. Theinvention defined in claim 1, wherein said trunnions each includea smooth cylindrical shank portion extending into one of said How portsin said cylinder and a sealing means circumferentally disposed on saidshank portion.

3. The invention deiined in claim l, wherein said pressure ports in saidtrunnions comprise axial bores and said pressure coupling means in saidtrunnions comprise counterbored sockets in said axial bores.

4. The invention dened in claim l, wherein each of said trunnionsfurther includes an externally threaded portion and an integral hex-headimmediately adjacent said threaded portion, said hex-head providingmeans whereby said trunnions may be turned-up snugly in said bores andadapted to engage said trunnion arms adjacent said bores whereby saidtrunnions are iixedly indexed with respect to said trunnion arms.

References Cited in the le of this patent UNITED STATES PATENTS1,021,887 Pollmiller Apr. l2, 1912 2,293,167 Overbeke Aug. 18, 19422,670,717 Armington Mar. 2, 1954 2,790,426 Mueller Apr. 30, 1957

1. IN A PNEUMATIC PISTON ACTUATOR INCLUDING A CYLINDER, A PISTON IN SAIDCYLINDER AND AN OUTPUT SHAFT CONNECTED WITH SAID PISTON; MEANS FORPIVOTALLY MOUNTING SAID CYLINDER AND CONNECTING SAID PISTON ACTUATORWITH SOURCES OF CONTROL PRESSURE COMPRISING A BRACKET, A PAIR OFDEPENDENT TRUNNION ARMS ON SAID BRACKET EACH HAVING A TAPPED BORE IN THEFREE END THEREOF, SAID BORES BEING COAXIALLY DISCYLINDER ADAPTED TO BEPLACED IN REGISTRY WITH SAID TAPPED BORES, AND A PAIR OF TRUNNIONSTHREADABLY SECURED IN SAID BORES AND ROTATABLY RECEIVED IN SAID FLOWPORTS, EACH OF